/*
    ** listener.c -- a datagram sockets "server" demo
    */

    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <errno.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>

    #define MYPORT 4950    // the port users will be connecting to

    #define MAXBUFLEN 100

    int main(void)
    {
        int sockfd;
        struct sockaddr_in my_addr;    // my address information
        struct sockaddr_in their_addr; // connector's address information
        socklen_t addr_len;
	int numbytes;
        char buf[MAXBUFLEN];

        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
            perror("socket");
            exit(1);
        }

        my_addr.sin_family = AF_INET;         // host byte order
        my_addr.sin_port = htons(MYPORT);     // short, network byte order
        my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
        memset(&(my_addr.sin_zero), '\0', 8); // zero the rest of the struct

        if (bind(sockfd, (struct sockaddr *)&my_addr,
                                              sizeof(struct sockaddr)) == -1) {
            perror("bind");
            exit(1);
        }

        addr_len = sizeof(struct sockaddr);
        if ((numbytes=recvfrom(sockfd,buf, MAXBUFLEN-1, 0,
                           (struct sockaddr *)&their_addr, &addr_len)) == -1) {
            perror("recvfrom");
            exit(1);
        }
	//Das als MessageBox wenn ein Paket empfangen
        printf("got packet from %s\n",inet_ntoa(their_addr.sin_addr));
        printf("packet is %d bytes long\n",numbytes);
        buf[numbytes] = '\0';
        printf("packet contains \"%s\"\n",buf);
        close(sockfd);

        return 0;
    }

Ich hoffe jemand kriegt das hin. Vielen Dank im Voraus

Microsoft hat sich auch mit dem Portieren beschäftigt:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/porting_socket_applications_to_winsock.asp

Mein Prog sieht jetzt folgendermaßen aus:

/* 
    ** listener.c -- a datagram sockets "server" demo 
    */ 

#include <iostream>
#include <stdlib.h>
#include <winsock.h>

    #define MYPORT 4950    // the port users will be connecting to 

    #define MAXBUFLEN 100 
using namespace std;

int main(int argc, char *argv[])
{
WSAStartup();
   int sockfd; 
        struct sockaddr_in my_addr;    // my address information 
        struct sockaddr_in their_addr; // connector's address information 
        socklen_t addr_len; 
    int numbytes; 
        char buf[MAXBUFLEN]; 

        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { 
            perror("socket"); 
            exit(1); 
        } 

        my_addr.sin_family = AF_INET;         // host byte order 
        my_addr.sin_port = htons(MYPORT);     // short, network byte order 
        my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP 
        memset(&(my_addr.sin_zero), '\0', 8); // zero the rest of the struct 

        if (bind(sockfd, (struct sockaddr *)&my_addr, 
                                              sizeof(struct sockaddr)) == -1) { 
            perror("bind"); 
            exit(1); 
        } 

        addr_len = sizeof(struct sockaddr); 
        if ((numbytes=recvfrom(sockfd,buf, MAXBUFLEN-1, 0, 
                           (struct sockaddr *)&their_addr, &addr_len)) == -1) { 
            perror("recvfrom"); 
            exit(1); 
        } 
    //Das als MessageBox wenn ein Paket empfangen 
        printf("got packet from %s\n",inet_ntoa(their_addr.sin_addr)); 
        printf("packet is %d bytes long\n",numbytes); 
        buf[numbytes] = '\0'; 
        printf("packet contains \"%s\"\n",buf); 
        close(sockfd);
        WSACleanup(); 
  system("PAUSE");	
  return 0;
}

Muss ich noch eine lib einbinden?

WSADATA wsa;

WSAStartup(MAKEWORD(2,0),&wsa);

..damit forderst du an, das du gerne Winsock Version 2.0 verwenden möchtest und kriegst in der WSADATA-Struktur noch irgendwelchen Kram geliefert, mit dem man z.B. prüfen könnte, ob Version 2.0 auch verfügbar ist..

Microsoft hat die ganzen Winsock Funktionen auch dokumentiert:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/wsastartup_2.asp